This invention relates to an automatic load-leveling pump for use in combination with conventional air adjustable shock absorbers or air bags.
Currently, automotive vehicles are available with either air or hydraulic automatic load-leveling systems. An automatic system, such as is disclosed in U.S. Pat. No. 4,017,099, uses conventional air shocks with an electrically powered air compressor to extend the shocks and electronic height sensing to control the amount of air pumped into the shocks by the compressor. Such systems are complex, costly and they constitute a power drain on the vehicle electrical system. Hydraulic load-leveling systems, such as are disclosed in U.S. Pat. Nos. 3,653,676 and 3,649,044, use engine-driven or electric motor-driven hydraulic pumps to pump hydraulic fluid into the rear shocks. Because of the incompressibility of the hydraulic fluid a separate gas accumulator or a gas-filled shock is necessary to soften the ride characteristic. Mechanical height sensing controls the amount of fluid pumped into the shocks. Also available are self-pumping load-leveling shock absorbers whose pumping action is powered by the relative motion of the vehicle frame and axle. Such self-pumping shocks are complex and costly and suffer from reduced pumping efficiency as the shock absorber is extended.